1. Field of the Invention
The invention relates to a radial piston-type pump which is provided with means to discharge oil which accumulates in the housing into the suction line of the pump.
This invention relates, in greater detail, to a radial piston-type pump with a non-rotating control pin projecting into a cup-shaped housing. A pivoted cylinder block is arranged on the control pin and is designed to include one or more radial cylinder holes which - when the cylinder block is rotating - are alternately connected with a suction line and a pressure line. Pistons are included which are guided so that their end surfaces, which project to the outside, rest against a stroke ring eccentrically arranged relative to the control pin.
2. Description of the Prior Art
From the Swiss patent CH-PS 377,035 a radial piston-type engine is known which is designed with a non-rotating control pin one end of which is staggered relative to the pump axis. A cylinder block is rotatably disposed on this end. This cylinder block is designed with cylinder holes which -- when the cylinder block is rotating -- are alternately connected via chambers with the suction line and the pressure line arranged in the control pin. The pistons guided in the cylinder holes are of concave design at their end surfaces projecting to the outside, and abut the cupshaped inner wall of the housing above roller bodies arranged in these concave groovings, which inner wall serves as a piston stroke curve at the same time. When the pump is in operation, the pump housing rotates, thus causing -- via the roller bodies -- the cylinder block to follow the rotational movement owing to the concave end surfaces of the pistons. In this process the eccentric arrangement of the cylinder block causes the stroke movement of the pistons at the cylinder holes.
In such pumps leakage losses occur at the place where the cylinder block is arranged on the control pin, and in the piston guides. The pressure medium, oozing out of the pump circulation system through the crevice between these members, accumulates in the housing, thus filling it. If this pressure medium is not discharged, as is done in the device according to the Swiss patent CH-PS 377,035, it will become the subject of turbulences due to the moving pump members when the pump is in operation. The turbulences, which are very strong on account of the heterogeneity of the movements of the single pump members, cause loud noises and cause the rotational movement of the rotary members to slow down, resulting in a lower delivery rate for the pump. In addition, these turbulences produce underpressure areas, causing cavitation which leads to noise development and damage to the members.